Laura misses Richard but fancies a night out. The rugby lads are knackered but on for a dance. The beer flows in the Sari. At 11.30pm Hannabeth hears a bang: is that a firecracker? Then the sky falls in

Saturday afternoon and a mobile phone bleeps inside a kit bag. The owner is playing football on a pitch in Surrey. "I am wound up thinking about you," says a text message sent from the other side of the world. "Missing you and your ways loads. Being away from you has made me realise how much I love you." The sender is thousands of miles from home, on the island of Bali, having a ball. Laura France has gone travelling, spending the money she saved by working Saturdays at a shop in Sheffield.

A little cash goes a lot further in Bali, so Laura, 18, and her best friend Natalie Perkins, 20, have decided to stay on for longer than planned. The beaches are long and white, the forests lush, the nightlife energetic, but Laura still has her new boyfriend, Richard, on her mind. He won't reply to her message for a while yet, not until his match ends; in the meantime, seven hours ahead in Bali, she and Natalie are ready to party. They've already phoned home, ending the call with happy shouts: "Have to go. We're off out now!"

Kuta Beach is full of rugby players. This is the end of the Australian season, traditional time for teams to go on a weekend away. The Dolphins from Coogee Beach are here, so are the Kingsley Cats from Perth, and the Platypi from Forbes, a farming town inland from Sydney. The Aussies hop on a flight to this island like Brits going to Ibiza, but they are not the only athletic drinkers around. The annual Bali Tens tournament has attracted 16 teams, including the Hong Kong Vandals and the rugby team from Singapore Cricket Club, both mainly made up of British expatriates.

"There is easy transportation from the hotel to the nightlife of Kuta," says a tournament website, which recommends the Sari Club. "Everybody is guaranteed to have a good time and waste a few brain cells."

Dozens of players have left their families back at the hotel to dance under the Sari's thatched roof. The place is packed with big blokes, drinking large quantities of Bintang beer. Those who can't squeeze inside are in Paddy's Bar, just across the busy street, watching barmen juggle bottles. Plastic palm trees have been planted in oil drums and Irish flags hang on the walls.

Aldo Kansil pushes through the crowd in Paddy's and orders a drink. The 20-year-old is barred from the Sari because he is not a foreigner. He comes from Lombok, the next island along, but has been in Bali on business, selling building materials. This is his first visit, so he is soaking up the atmosphere on Jalan Legian, the narrow thoroughfare close to the beach and location of most of the bars and clubs.

There's a traffic jam outside, because two vans are blocking the way. One of them is parking right outside the Sari just as Emma Cort, a 27-year-old teacher from Wales, steps on to the street. She's been at a wedding, then shopping with a friend. The two women were planning to go out dancing, but one of them has a migraine and they both feel overdressed among the young clubbers and backpackers. So they hail a taxi instead, and head home.

The traffic begins to move again as one of the two vans drives away, carrying eight men. The other, a Mitsubishi L-300 standing outside the Sari, is empty.

The road is busy with people, one of whom stoops to put down a white plastic bag close to the entrance to Paddy's. He walks away. Those who remember him later will say he looked nervous. They will blame him for the small explosion that sends a tongue of flame into the air and makes enough noise to bring the drinkers in the Irish bar out on to the street. Some are frightened, some just curious.

It's about 11.30pm. Inside the Sari Club, Hannabeth Luke hears the bang and assumes someone is fooling around with a firecracker. She carries on dancing as others head for the door, including her boyfriend Marc Gajardo, who has taken offence at the song the DJ is playing. The 30-year-old surfer from Cornwall does not care for "Believe" by Cher, so he goes outside for fresh air, not far from the parked van.

Seconds later the C4 military plastic explosive packed into the roof of the vehicle is detonated by remote control or a timer.

The blast can be heard five miles away, as gas cylinders stored in the club create a fireball that shoots through the roof of the Sari high into the air. Bodies are propelled into the sky and come down in pieces, as it rains shattered glass and debris.

"There was a blinding white light," one of the few survivors will say later. "It was like the sky fell down."

Hannabeth Luke feels her feet sucked from under her. The walls of the club collapse, the roof caves in, and she hits something solid. Everything is dark apart from the flames, but the sky appears over her head. The ground shakes. Coming to her senses she sees a dangling electric wire and uses it to pull herself over a wall at the back of the building. Others clamber over lifeless bodies to reach narrow exits.

An Australian man cradles a woman in his arms as she moans. "I can't breathe, I can't breathe." Then she dies. Out in the street Hannabeth calls Marc's name, but knows within herself that he is dead.

Barrie King, 46, a pilot from Manchester, lies on the floor, wriggling his fingers and toes, slowly realising he's all right apart from a terrible ringing in his ears. Three women lie side by side on the floor, motionless. They are naked, their clothes blown off by the blast. James Woodley, a backpacker, crawls through the fallen roof and runs across hot metal, through burning bamboo and straw. The place where he was sitting a few moments ago has been buried under metal. "I had gone on to the dance floor about 20 seconds before it blew up. If I'd stayed in my seat there was just no way..."

Outside, the survivors are confronted by a wall of flame, as vehicles burn. Motorcycles weave through the bodies of the injured or dying. Some corpses are limbless, some decapitated. Four blackened bodies sit upright in a ruined car. A man with no feet drags himself along the street with his arms. A woman runs as her clothes burn. A man dressed only in underpants staggers about, charred and bloody, with his shoes in his hands. Those who can walk just wander, dazed, looking for friends, calling out.

Richard Poore, a television director from New Zealand, who failed to get in to the crowded club, sees "a procession of people covered in blood ... people with glass shards embedded in them ... women with their hair on fire and their bodies on fire". The sky is glowing orange. Emma Cort looks out of the taxi on the Kuta Beach Road at "a massive plume of smoke" which makes her think of a plane crash. Someone says a power station has blown but she knows there are no big power stations on Bali. "It must have been a bomb."

Hundreds of foreigners head for the beach, just to get away. They will spend the night there, feeling it safer. Many Indonesians make for the bomb site, to look on in horror or to help.

Aldo Kansil staggers out of the ruins of Paddy's Bar into Jalan Legian, then collapses. Strangers haul him into a taxi, one of dozens heading for Sanglah hospital in the capital Denpasar. A third bomb has gone off there, outside the US consulate. Other victims are carried on the back of mopeds.

"I didn't recognise the face, only the voice," Aldo's brother-in-law will say later at the hospital. "He looked like his flesh was still burning. He couldn't breathe very well. He was trembling a lot. I couldn't talk. I could only cry."

Sanglah is overcrowded. It can't cope with the sudden arrival of 300 very badly injured people. "People are dying because there's no blood, no bandages, no surgical scalpels," says Maria Jakes, a medically trained volunteer. "It's an absolute nightmare. People are lying around bleeding and there's nothing we can do for them."

The sun rises. The sight it reveals is obscene. The Sari Club is now a black, water-filled crater. The remaining scraps of wall are stained with blood. Buildings nearby have been blown to rubble or razed by fire. Paddy's Bar is a twisted mess of steel, concrete and corrugated iron. Shreds of Irish flags hang in the branches of blackened trees. Tourists and locals alike climb over the ruins, taking photographs: a leg lying in the street, a severed hand.

At the hospital, the television cameras are on as the body bags are sorted: European and Asian, male and female. The corpses are piled high, some in the corridors or heaped on blocks of ice in the foyer, as temperatures climb. A German woman sits and weeps, repeatedly: "My friends are dead."

Emma Cort gives blood, responding to an urgent appeal. Foreign patients are being evacuated to Australia or Singapore, but the locals turn out to be not so lucky. Aldo Kansil will not receive any medical treatment for hours, despite suffering intense pain. Dozens of other Balinese will also have to wait for help.

The rugby teams are conducting a terrible roll call. Nine players or supporters from the Hong Kong Vandals are missing presumed dead, including one woman. "It is complete chaos down there so anyone could be in hospital or unaccounted for somewhere else," says a club official.

The Singapore Cricket Club has lost five members and knows that three more are definitely dead. The 11 surviving Kingsley Cats have vowed not to return to Australia until they find their seven missing team-mates. "Realistically," says the coach, "we expect most, or at least half, or all, the blokes to be located somewhere in that morgue."

The names of the confirmed dead are written on a big white board in Sanglah hospital. There are also lists of those who have been discharged, or flown home. But the longest list of all is of those who are still missing.

One name on the board is that of Ian Stafford, 41, of County Durham – but Mr Stafford is alive, and he's standing in the hospital. He watches mortuary staff lift the lid of a silver box that supposedly contains his own body, and sees instead the face of his friend Ian Findley, 55, who's been wrongly identified because of a hotel bill in his pocket. The two men were at the front door of the Sari Club, one behind the other, when the big bomb went off. "Ian saved my life," says Mr Stafford. "Without him shielding me from the blast I would almost certainly be dead."

Back in England, where it is still Saturday evening, a woman is trying to call her brother, Paul Husey. The 46-year-old does not answer his mobile. He is in a body bag on ice at Sanglah hospital, with both his legs missing.

The young Queens Park Rangers footballer Richard Brady has just come off the pitch, and reads the loving message sent by his girlfriend Laura. He misses her too, and taps out a reply. But five hours have passed since the happy teenager sent her text. Laura is thought to have been buried under the collapsing roof and walls of the Sari Club. She is one of the 187 known dead. "He is devastated," a friend will say as Brady and the world try to come to terms with the horrors of Kuta Beach. "He's just at home crying. He can't understand why this has happened."